Molecular signalling underlying developing muscular tube extension
Many structures in our bodies, like the oesophagus and intestines, are tubes. Each starts off as very short structures, but by birth have lengthened substantially. But what drives these tube extensions? Most of our cells have a singular cilium protruding from its surface acting like an antenna waiting to receive signals. These ciliary structures must first receive signals from Hedgehog proteins to first create a layer of smooth muscle (green) in structures like the oesophagus (pictured). This muscle starts to exert mechanical forces onto mesenchymal cells – a type of stem cell – and triggers the accumulation of a protein called YAP (red) which promotes cell proliferation, resulting in tube elongation. By removing the cilium gene CILK1 (bottom row), smooth muscle organisation was disrupted and the amount of YAP was reduced in the intestines, but also in the developing oesophagus showing that Hedgehog signalling to the cilia is the tube driver.
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